There is currently and there has been for some time a need for a simple, comparatively inexpensive reliable fire extinguisher that operates automatically when there is a fire. To be effective such an extinguisher needs to be sensitive enough to be operated during the initial stages of a fire in order to effectively extinguish the fire and to avoid any substantial fire damage. Unfortunately, such systems in the past that were sensitive enough to detect a fire in its very initial stages were also prone to activation when there was no fire. For instance, many such systems could be falsely activated by heat even though there was no actual fire.
This, of course, placed severe limitations on the types of environments in which the system could be utilized. For instance, such systems could not be practically used in environments where there was high heat or open flame or worse yet both high heat and open flame. This later situation exists in many kitchens when cooking is taking place. This combination of high heat and open flame makes it very difficult to provide a fire extinguishing system that is practical which can operate in such an environment.
A system that can be falsely activated is at best inconvenient since the system must be reset so that it can be activated again. In addition, many systems must be recharged or the like so that they can supply a suitable fire extinguishing media. This means that such systems are inoperable for a period of time after they have been used. An improperly activated fire extinguisher system can also result in property damage such as by a fire extinguisher chemical getting into food or machinery. This also requires appropriate cleaning in the vicinity of the extinguishing system. In addition, an improperly activated system can result in the need for a place of business to be temporarily closed while the system is being reset and or reconditioned.
Of course, the consequences of a fire extinguisher system failing to operate can be as bad, or even much worse, than a system that operates prematurely. A system that fails to operate can result in serious property damage and even death. The consequences tend to be worse if the fire extinguishing system is in a location where a fire is likely to go undetected for some period of time.
Fire extinguishing systems in the past have also been liable to degrade in their reliability with time and hence have required periodic checking and maintenance. Most fire extinguishing systems use some type of valve apparatus and valve activation apparatus and this apparatus can degrade with time and is difficult to check and maintain.
This invention overcomes these problems associated with previous fire extinguisher systems. This invention is sensitive and able to detect the initial stages of a fire and yet it is not subject to false activation even when it is in an adverse environment. It is also simple and reliable and its reliability does not degrade significantly with time.
With this invention the extinguishing action is initiated if a fire is sensed simultaneously by a temperature sensor and a light sensor. Detection of an abnormally high light or infrared radiation level is considered sufficient evidence of a fire. Since cooking stoves typically emit considerable heat, detection of high temperatures alone is not satisfactory for identifying a fire condition.
A need for fire detection and automatic suppression exists in all homes, but is particularly useful in units inhabited by the handicapped and elderly. This automatic fire extinguisher accomplishes its task without human intervention and not only warns of a danger but actively neutralizes that danger.
This invention is based on the principle that fires typically emit both heat and light/infrared radiation simultaneously. Accurate discrimination of excessive levels of these parameters allows initiation of a chain of events ending in the release of a fire suppression agent.
The temperature sensing device has an electrical output proportional in some way to the level of the sensed ambient temperature. In a like manner, the light or infrared radiation sensor has an electrical output proportional to the intensity of the viewed light or infrared radiation. When the ambient conditions drive the sensor outputs beyond normal or typical limits simultaneously, then a condition is realized whereby a stored energy source is called upon to actuate a release mechanism.
Previous stored energy sources for activating fire extinguishers have not been satisfactory since they have been difficult to initiate or activate. Such stored energy sources have also not remained reliable over extended periods of time. It has been unexpectedly determined that chemically stored energy in the form of a solid propellant located within a cartridge similar to the cartridge for a firearm overcomes these problems.